Means of propulsion for ships



July 20,1926. 1,593,526

F. T. EDGECOMBE MEANS OF PROPULSION F03 SHIPS Filed April 4,1922 3 Sheets-Sheeti FIG. I.

l kzom/m 77mm foam:

5 his Arm meys uly 20 1926. 1,593,526

F. T. EDGECOMBE MEANS OF PROPULSION FOR SHIPS Filed April 4. 1922 v s SheetsShee t 2 s V k JAN/EN 7'08:-

by his Arm/hays v finommr 771mm [DGECOMEE Patented July 20, 1926.

FREDERICK THOMAS nnenoolvrnn, or DUMBARTON, SCOTLAND.

MEANS OF PROPULSION FOR SHIPS.

- Application filed April 4, 1922, Serial No.'549,512, and in Great Britain April 16, 1 921.

The invention has for its object to provide improved means ofpropulsion and manoeuvring, more particularly for shallow draught vessels, which, while offering high propulsive efficiency, is not seriously affected'by varying draught and consequent varying immersion.

Accordingto the well known stream line theory, a ship in passing through water. experiences pressure at the forward end owing to departure of the stream line frbnl parallelism with the keel. Abaft the broadest part of the vessel the particles of water eXert pressureon the closing in form of the vessel. The pressures on the forward end tend to-retard advance, those on the after end to assist it. I

In a frictionless fluid with no surface disturbance'these pressures would be equal and there would be no resistance. Undcr ordinary ship conditions, these pressures at the bow and stern do not balance and the excess of the bow pressuresover those at the stern, forms a substantial part-of-the resistance of 1 the vessel.

l/Vhen propellersare placed'close to the after part of the vessel, in this region of replacement, and are made to give sternward momentum to large quantities of water,there is a reduction of the forward pressure on the after part of the ship, and'a consequent augmentationof resistance. It is well known that if-screw propellers I could be so situated that they acted in an area clear-of this-region of replacement of the stream lines, there would be little or no reduction of the forward pressure and a large gain in propulsive efficiency. Hitherto it has not been practicable to attain this condition without large collateral losses.

This invention has for its object to provide that the propelling agent shall act in a position sufliciently remote from the region of interference that there is no disturbed water (or substantially none) at, and axially abaft, the propelling agent.

The improved propelling unit consists of a pair of wheels each of which is provided with a number of arms arranged around an axisparallel, or substantially so, with the middle line of the vessel. In other Words the shafts carrying the wheels are in substantial parallelism with the center line of the hull. These arms carry vanes at their outer end, which'vanes are in the form of a multiple helix of short length. The wheels have their vanes of opposite pitch, are oppositely rotated, and to .obtainthe maxi.- mum manoeuvring power should preferably be arranged side by side with the direction of rotation for going ahead, outward on top relatively to one another.

The wheels are carried on a rigid above water extension of the ship abaft or elsewhere, such as a counter or sponsons and so positioned for height above the water, that only a :part of the periphery below the axis is immersed; preferably the vanes should be just immersed when the vessel is at full speedand at normal draught. I

A propelling unit consisting of a .pair of propelling agents is shown in front and side elevation in Figures 1 and 2, of three ac companying sheets of drawings, while Figures 3 and 4, are diagrams illustrative of-the conditions hereinbefore set forth which, it is necessary for efiiciency, shall be fulfilled. Fig. 5 is a plan view showing the location of the vane wheels.

In thiseXample two A, B of the improved propelling wheels are arranged upon an above water-after projection F of the ves sel E and abaftthe rudderG. The :propel ling wheels are positioned side bysidet-hat is, in the same.transverse..planeand with their blades of opposite pitch, the llellX .of

the starboard wheel being rrighthand while that of the port wheel is :left hand, so that when they are propelling the vessel ahead the upper partstturn outwards and away from each other as indicated by the arrows in Figure 1. This relative arrangement of the pitches of the wheels is found of considerable advantage in manoeuvring.

It will be seen that the wheels lie a considerable distance aft of the aftermost sub merged portion of the structure of the ship (indicated by dotted lines in Figure 2) a distance equal to about of the overall diameter of the wheel. It will be further noted that the diameter of the wheels is substantially greater than the draught of the vessel.

Thus the vessel comprises a hull partly immersed along part of its length, having as a component part a rigid above-water projection aft of its immersed portion. The projection carries the vane wheels, together with their shafts or driving means, bearings and supports.

The vane wheels are, of course, independ ently operated in order to obtain the manoeuvring facility above mentioned.

The necessity in the pursuit of high ethciency for the positioning of the wheels as hereinbefore set forth, is amply upheld by the plotted chart, Figure 3, which is the plotted result of actual experiment. In this chart, the ordinates represent percentages of efficiency and augmentation, and the abscissae distances in feet that the wheel is positioned abat't the aftermost submerged portion of the vessels hull.

The upper curve C indicates the propul sive etlicieney (effective H. P.) (shaft H. P.)

while the lower curve D represents the percentage augmentatiol'i of resistance by propeller action.

In the sectional half-plan hull dia ram of Figure 4-, the propelling wheel A is shown as placed abaft the disturbed area (indicated by dotted lines) caused by and moving with the moving hull E.

\Vhat I claim is 1. In a self-propelling vessel comprising a hull partly immersed along part of its length, a fixed above water extension of the vessel, and shafts in substantial parallelism with the center line of the hull mounted upon said extension, in combination with vane wheels at the after ends of the shafts, the height of said extension above the water being sufficient to permit only part of the vane wheel periphery below the axis to be immersed, and said extension being adapted to position the vane wheels substantially clear of the stream line replacement region abaft the vessel.

2. In a self-propelling vessel comprising a hull partly immersed along part of its length, a fixed above water extension of the vessel, and shafts in substantial parallelisn'i being sufiicient to permit only part of the vane wheel periphery below the axis to be immersed, and said extension being adapted to position the vane wheels a distance equal to at least 75% of the overall diameter of the wheel aft of the aftermost submerged portion of the vessel.

3. In a self-propelling vessel comprising a hull partly immersed along part of its length, a fixed above water extension of the vessel, and shafts in substantial parallelism with the center line of the hull mounted upon said extension, in combination witn vane wheels at the after ends of the shafts, the height of said extension above the water being sufficient to permit only part of the vane wheel periphery below the axis to be immersed, and said extension being adapted to position the vane wheels substantially clear of the stream line replacement region, abaftthe vessel, the diameter of the wheels being substantially greater than the draft of the vessel.

4. In a self-propelling vessel comprising a hull partly immersed along part of its length, a fixed above water extension of the vessel. and unconnected independently operated shafts in substantial parallelism with the center line of the hull mounted upon said extension, in combination with vane wheels at the after ends of the shafts the height of said extension above the water being sutiicient to permit only part of the vane wheel periphery below the axis to be immersed, and said extension being adapted to position the vane wheels substantially clear of the stream line replacement region abaft the vessel.

In testimony whereof I have signed my name to this specification.

FREDERICK THOMAS EDGECOMBE. 

